The present invention relates to a resin intake manifold which is provided with an intake air inlet pipe, an intake vessel connected to an intake air supply via the inlet pipe, and a plurality of outlet pipes which connect the intake vessel to cylinders of an internal combustion engine, and to a manufacturing process of such a resin intake manifold.
The cylinder head of a multi-cylinder internal combustion engine is connected to an intake manifold for supplying intake air into combustion rooms of the respective cylinders. The intake manifold generally includes an inlet pipe (intake pipe) which is connected to an intake air supply such as a carburetor, an intake vessel (chamber, surge tank) which is supplied with intake air through the inlet pipe, and a plurality of outlet pipes (branched pipes) which connect the intake vessel to the cylinders of the internal combustion engine. The intake manifold is commonly made of a molten resin composition, chiefly due to its superior properties providing lightweight, good insulation, easy manufacture, and more freedom in terms of design.
Such a resin intake manifold is manufactured, for example, by separately casting the intake vessel, the inlet pipe, and the outlet pipes, and then by coupling these components together. This manufacturing process incorporates separate members to make the intake manifold, and thus the mold used to cast each member can be made compact. However, the drawback is that the number of molds becomes large, and it increases the number of steps to couple these components together. This might increase cost or result in low productivity.
An example of this process is described below based on an intake manifold for a three-cylinder internal combustion engine. Manufacture of this intake manifold requires a total of five kinds of molds, one for the inlet pipe, three for the outlet pipes, and one for the intake vessel, so that these components can be separately casted. As a result, coupling of these components requires four steps. Further, each components may be made in the form of half-parts. As the term is used herein, the half-parts are halves of a component which make up a pair of first half-part and second half-part. The half-parts, i.e., the first half-part and the second half-part are combined to form the component. Therefore, in this case, a total of 10 kinds of molds will be required, and coupling of these half-parts requires additional five steps. Thus, this process is not suitable when high productivity is sought, as in the case where resin intake manifolds of a mass-produced engine are manufactured.
Further, since the intake manifold has a complex structure incorporating a large number of components, it is intrinsically difficult to cast it from a molten resin composition in integral form. Thus, there has been proposed a method in which half-parts of the intake manifold itself are casted and later combined. That is, there has been attempts to manufacture the resin intake manifold by casting its half-parts in different molds, and combining these half-parts later. However, due to the configuration of the conventional intake manifolds, the shape of the half-parts becomes a so-called xe2x80x9cundershapexe2x80x9d, and the half-parts are stuck and cannot be easily removed out of the mold. Thus, this method too suffers from low productivity.
The present invention was made in view of the foregoing problems and an object of the present invention is to provide a resin intake manifold of a configuration which enables efficient production, and to provide a manufacturing process of such a resin intake manifold.
In the present invention, as the term is used herein, xe2x80x9cresinxe2x80x9d refers to those molding materials which can flow into a mold when melted to become a molten material at a high temperature, and which become sufficiently strong when solidify. Accordingly, the resin used in the present invention is not just limited to so-called polymer resins such as plastic.
In order to achieve the foregoing object, a process according to the present invention is for manufacturing a resin intake manifold including an intake vessel which is supplied with intake air through an intake air inlet pipe, and a plurality of outlet pipes which are connected on one end to respective cylinders of a multi-cylinder internal combustion engine and on the other end to the intake vessel, the outlet pipes being connected to the intake vessel so that an external wall of the outlet pipes on this end is integral with an external wall of the intake vessel, and having a configuration extending from the intake vessel in a curve with a curve angle in a range of larger than 90xc2x0 and not larger than 180xc2x0 in a direction away from the intake vessel, and continuously extending away from the intake vessel, the process comprising the steps of molding a pair of half-parts of divided halves of the intake vessel and the outlet pipes divided along a direction of a pipe axis, and then coupling the half-parts on their coupling faces.
It is preferable in this manufacturing process that the pair of half-parts are molded by injection molding, and then coupled to each other on their coupling faces in a mold, using a die rotary injection method (DRI method) or a die slide injection method (DSI method).
According to this process, by the defined positional relationship between the intake vessel and the outlet pipes, the half-parts or the resin intake manifold produced by the DRI method or DSI method will not be stuck on the mold when they are removed.
That is, contrary to common resin intake manifolds which with complex configurations are manufactured into finished products by assembling a large number of parts, the resin intake manifold can be manufactured only by coupling two parts (i.e., a pair of half-parts), and the half-part will not be stuck on the mold. As a result, the resin intake manifold can be efficiently manufactured.
Further, when adopting the DRI method or DSI method in the foregoing manufacturing process, the curve angle of the plurality of outlet pipes may be in a range of not smaller than 120xc2x0 and not larger than 180xc2x0.
The curve angle in this range enables the resin intake manifold to be designed with a predetermined length of the outlet pipes while maintaining the size of the resin intake manifold compact. Effects of this are: 1) intake air can be supplied to the respective cylinders of the internal combustion engine more desirably; and 2) the resin intake manifold can be stored in an engine room of a relatively small size.
In order to achieve the foregoing object, a resin intake manifold according to the present invention includes an intake vessel which is supplied with intake air through an intake air inlet pipe, and a plurality of outlet pipes which are connected on one end to respective cylinders of a multi-cylinder internal combustion engine and on the other end to the intake vessel, wherein: the resin intake manifold is composed of a pair of half-parts of divided halves of the intake vessel and the outlet pipes divided along a direction of a pipe axis, which are coupled to each other, and the outlet pipes are connected to the intake vessel so that an external wall of the outlet pipes on this end is integral with an external wall of the intake vessel, and extend from the intake vessel in a curve with a curve angle in a range of larger than 90xc2x0 and not larger than 180xc2x0 in a direction away from the intake vessel, and continuously extend away from the intake vessel.
It is preferable in this resin intake manifold that at least one of boundary areas of the intake vessel and the outlet pipes on the coupling face of one of the half-parts has a raised portion, and the coupling face of the other half-part has a recessed portion to fit the raised portion.
By thus providing the raised portion and the recessed portion which fit into engagement on the coupling faces of the pair of half-parts, the strength of coupling of the half-parts can be improved.
For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.